A Topological Study of the Transition States of the Hydrogen Exchange and Dehydrogenation Reactions of Ethane on a Zeolite Cluster

NORA B OKULIK; REINALDO PIS DIEZ; ALICIA H JUBERT

JOURNAL OF PHYSICAL CHEMISTRY A

AMER CHEMICAL SOC

Año: 2004 vol. 108 p. 2469 - 2474

1089-5639

The transition states of the hydrogen exchange and dehydrogenation reactions of ethane on a zeolite acid site are calculated using the density functional theory and analyzed with the atoms-in-molecules method. The transition state for the hydrogen exchange reaction is characterized by a slightly ionic interaction between a distorted H-ethonium structure, C2H7+, and a negatively charged zeolite cluster. No free carbocation is found. The dehydrogenation reaction, on the other hand, shows a transition state with three well-defined fragments, namely, an ethyl cation, C2H5+, a negatively charged zeolite cluster, and a H2 pseudomolecule, in which the H-H bond is somewhat larger than the equilibrium value in H2. The interaction between those fragments can be described as a closed-shell one, typical of rather ionic systems.